Within the IP (Internet Protocol) Multimedia Subsystem (IMS) as defined by 3rd Generation Partnership Project (3GPP) Session Initiation Protocol (SIP) defined by the Internet Engineering Task Force (IETF) is used for controlling communication. SIP is an application-layer control protocol for creating, modifying, and terminating sessions with one or more participants. These sessions may include Internet multimedia conferences, Internet telephone calls, and multimedia distribution. Members in a session can communicate via multicast or via a mesh of unicast relations, or a combination of these. Session Description Protocol (SDP) is a protocol which conveys information about media streams in multimedia sessions to allow the recipients of a session description to participate in the session. The SDP offers and answers can be carried in SIP messages. Diameter protocol has been defined by IETF and is intended to provide an Authentication, Authorization and Accounting (AAA) framework for applications such as network access or IP mobility.
Generally, for properly establishing and handling a communication connection between network elements such as a user equipment and another communication equipment or user equipment, a database, a server, etc., one or more intermediate network elements such as control network elements, support nodes, service nodes and interworking elements are involved which may belong to different communication networks.
Mechanisms exist to transfer subscriber related information between a proxy call state control function (P-CSCF), a serving CSCF (S-CSCF) and a home subscriber server (HSS). The subscriber related information includes so-called ‘Display Name’ parameter which represents a preferred name of a calling party. In addition to displaying the calling number, the display name can be presented to the called party
However if the display name is updated at the HSS, the old display name is still displayed to called parties on all newly initiated calls until a registration/re-registration of the calling subscriber takes place and the subscriber related information at the P-CSCF is updated.
Subscriber related information is sent to a P-CSCF at the time of registration from a S-CSCF in a 200 OK SIP response. In case there is a change in the display name of the subscriber at the HSS in the interim, the change (new display name) is communicated from the HSS to the S-CSCF. However the updated information does not reach the P-CSCF until the time of a re-registration, which means that the data contained in the user profile for the subscriber is not consistent at the P-CSCF and the S-CSCF.
Until the next re-registration occurs, the older display name is used for all calls that are established by the subscriber. For example, if a re-registration timer is set to 24 hours, it can take up to 24 hours before the new display name is shown to called parties.